1. Field of the Invention
The present invention relates to an improved billiard cue and more particularly to an integral or one piece cue tip exhibiting high durability, a high coefficient of friction on the surface contacting the billiard cue ball and good rigidity.
2. Background to the Invention
The cue or cue stick used for billiards is a multiple part instrument used to make carom or pocket billiard shots. These shots may require power or delicacy, and may be made off center on the cue ball to impart back, left or right spin to the cue ball. The combinations of weight and balance of a cue, the materials from which the cue is made, and the manner in which the parts, e.g. ferrule, cue tip, shaft and butt (if a jointed cue) are connected, vary and strongly influence the ability of players to make shots. However, even the best quality cue cannot compensate for a badly worn cue tip.
Cue tips are pieces of shaped material attached to the cue end used to strike the cue ball. Generally, cue tips have been a piece of specially processed leather or other fibrous or pliable material. A cue tip made from relatively pliable material requires a player to make firmer shots to obtain a desired cue ball speed. However, pliable material compresses on contact with the cue ball, increasing the surface area in contact with the cue ball allowing more spin, draw or follow to be applied to the ball than a firm, less pliable tip allows. Additionally, a pliable tip holds chalk better than does a less pliable tip, and chalk increases the coefficient of friction between the cue tip and the ball, which aids in applying spin, draw and follow to the ball. Unfortunately, highly pliable cue tips deteriorate and lose their shape more quickly than firm cue tips, and their playing characteristics degrade more quickly as a result. Traditional tip materials rapidly deform and "mushroom" after only a few hundred impacts, necessitating reshaping of the cue tip.
The shape of the cue tip is important. The portion of the surface of the cue tip intended for contact with the cue ball is initially shaped as a hemisphere, ideally with a radius of between 8 mm and 14 mm. Generally, the larger the radius of the contact surface of the cue tip, the greater the surface area available for application to the cue ball, enhancing application of spin, draw and follow to the cue ball. A smaller radius tip reduces the chance of a miscue. However, a smaller radius tip implies a smaller radius shaft and such shafts lack stiffness. This in turn limits reduction of the shaft radius and, implicity, the tip radius if the tip is to remain flush with the the shaft. As discussed above, the durability of the cue tip contributes directly to how long the tip maintains a hemispherical shape within the desired dimensions. Smaller diameter cue tips have been considered more durable.
To maintain a cue tip with a proper hemispherical shape and pliability has required regular attention to the condition of the tip. In commercial establishments, cues frequently exhibit badly worn cue tips, making play more difficult. The need to constantly chalk cue tips also demands the proprietor's careful attention to the condition of chalk blocks. The proper maintenance of a leather faced cue tip can require labor in removal, gluing and shaping, typically done in professional shops at some expense.
Alternative materials to natural leather have been considered and the rules of play for pocket billiards specify only that leather and synthetic leather tips be used for jump shots. Of particular interest is U.S. Pat. No. 5,016,877 to Lowery which teaches the use of polyurethane for cue tips. However, it is possible that several hundred types of polyurethane have been formulated for various functional attributes. The primary types of polyurethane have been generally categorized as coatings, foams, fibers and elastomers. Lowery identified three examples of material deemed suitable as a substitute for leather as cue tip material: Adiprene and Vibrathane, made by Uniroyal Chemical Company; and Mobay 4210, then made by Mobay Chemical Company (at the time of this writing Texin 4210, a product of Bayer Inc., Polymers Division, Pittsburgh, Penn.)
Adiprene and Vibrathane polyurethane are families of polyurethane elastomer products. Polyurethane elastomers are known for their resistance to abrasion, and are commonly used for shoe uppers and heels, encapsulation for electronic parts and automobile bumpers, among other applications. Texin 4210 is a polyurethane/polycarbonate blend thermoplastic. Lowery, while not specifying a particular version of Adiprene or Vibrathane for use, concluded that an appropriate polyurethane material for a cue tip would have a hardness of "from 55 to 85 Shore-D". The patent does not, however, discuss an appropriate coefficient of friction for the material nor does it discuss material resilience, that is the ability of the material to resume its original shape after deformation. Instead Lowery provided shaping of the cue tip, including a plurality of radial and parallel annular grooves to increase the area of contact between ball and cue tip upon tip and ball impact and tip deformation, thereby providing control when striking a ball obliquely.